Interact with ctx in transactionnal messages

Hi everybody,

I want to change the value of a ctx variable in a content bloc, but the syntax 

context.rtEvent.ctx.version = version

seems not to be allowed.

This way allows me to personnalize the content of several paragraphs in my email, depending on the data I receive.

Is it possible, and what's the syntax ?

Thanks for your help, I can of course explain more what I want exactly to do if necessary...

content bloc for example :

<%@ value object="startScript" %>

// default
var version = "Soutien2";

// change ctx node

context.rtEvent.ctx.version = version;

//debug
document.write(version);

<%@ value object="endScript" %>